and a vatican bombshell raising an enormous number of questions today. pope benedict today becomes the first pontiff in 600 years to announce retirement. ahead, what is behind this move? what does it mean for the church and what about the near constant speculation that the time may be near for the first american pope? and he may be one of the greatest heroes of our time and we're finally hearing his side of the story. we will bring you the first interview with the man who fired the shot that killed usama bin laden. >> tonight, i can report to the american people and to the world the united states has conducted an operation that killed usama bin laden the leader of al-qaeda, a terrorist responsible for the murder of thousands of men, women and children. puts all the things we love about sunday meals into each of her pot pies. like tender white meat chicken and vegetables in a golden flaky crust that's made from scratch. marie callender's pot pies. it's time to savor. >> we're back now to the developing manhunt for an ex-lapd officer turned triple murder s